Modern polymers and thermoplastics are extruded or molded into objects for use in a number of applications in the fields that include consumer, construction, automotive, and aerospace. Organic and inorganic mineral fillers in particle and/or fiber form may be mixed or blended with a polymer to create a polymer composite material which may display new and improved properties such as increased fire retardancy, increased modulus and hardness, thermal and electrical conduction, and a desired coloration. The distribution of the filler material in the polymer host of the composite should be as homogenous as possible so that the composite properties are not compromised or degraded. For example, too high of a weight percent of a filler in the composite, and/or lack of filler homogeneity in the composite, may result in a material that crumbles easily and is not processable into a useful object.
Carbon black (CB) is a filler material that is used to impart dark or black coloration in a polymer, and may also be used to create an electrically conductive polymer composite, such as those found in resettable fuses, and in radio frequency shielding applications. Carbon black is used in a variety of polymers, from olefins to polyesters, but may exhibit phase separation and aggregate formation which can negatively impact the composite properties due to the lack of miscibility of the fillers, and/or affinity for the polymer host. In particular, polyesters suffer from the aforementioned phase separation and segregation phenomena, and in many cases are unable to uptake sufficient useful amounts of CB to achieve the desired polymer composite properties. Therefore, it would be an advantage to have a melt-processable polyester CB composite, such as a polylactic acid (PLA) CB composite, that has improved CB filler/polymer homogeneity, and uses a lower percent by weight loading of CB in the composite to realize desired properties such as coloration.